First of all, fire up a terminal window and run the following command to update existing software packages.

sudo apt update && sudo apt dist-upgrade

Please note that if a new kernel is installed while running the above command, you need to reboot system in order to continue the upgrade process. Then open Software & Updates from Unity Dash or your favorite application menu.

Select the Updates tab and then at the bottom of window, change notification settings from For long-term support version to For any new version.

Click the close button. You will be asked to enter your password to apply the above changes, then issue the following command in terminal.

update-manager

If you are using Ubuntu 17.04, you will be notified that software is up-to-date and Ubuntu 17.10 is now available. Click the Upgrade button.

If you are using Ubuntu 16.04, you will be notified that software is up-to-update and Ubuntu 17.04 is now available. Click the upgrade button. You need to upgrade to Ubuntu 17.04 first and then follow the same steps to upgrade to Ubuntu 17.10. This is due to the fact that Ubuntu 17.04 is still being supported by Canonical and hasn’t reached end-of-life yet.

At the bottom of this file, change the value of Prompt from lts to normal.

Prompt=normal

Save and close the file. After that, run the following command to begin the upgrade process.

do-release-upgrade

If you are running Ubuntu 17.04, then follow the on-screen instruction to upgrade to Ubuntu 17.10. If you are running Ubuntu 16.04, then follow the on-screen instruction to upgrade to Ubuntu 17.04 first and then follow the same steps to upgrade to Ubuntu 17.10.